Touch Sensor Grounding via AC Signal for Water Detection Errors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Touch sensor panels of projected capacitive type face errors in detecting touches when coming into contact with high relative permittivity substances like water, as they fail to distinguish changes in capacitance caused by water from those caused by a finger, leading to potential misclassification of water contact as a touch.
Innovation Solution
A touch sensor panel configuration that includes a panel controller and a signal generation circuit capable of applying an AC signal to the ground, ensuring that all points except the ground are excited at the same potential, minimizing the potential difference between the touch sensor and surrounding components, thereby reducing false detection of high relative permittivity substances as touches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a touch sensor panel of projected capacitive type is used, then the robustness and design flexibility are improved, but the panel becomes susceptible to detection errors when coming into contact with high relative permittivity substances like water
Solution Approach 1:
The patent applies equipotentiality by connecting the case to ground and applying an AC signal to create a reference potential. This establishes a stable electrical reference that allows the system to distinguish between capacitance changes caused by water contact (which does not break the potential reference) versus actual finger touches (which do break the reference), thereby resolving the detection accuracy issue while maintaining robustness
2Measurement precision
If the case is electrically connected to ground with AC signal application, then the detection accuracy for distinguishing water contact from finger touches is improved, but the device complexity increases
Solution Approach 1:
The patent makes the case serve multiple functions: it acts as both the structural housing and an electrical reference potential source. By connecting the case to ground and applying the AC signal through existing components, the system reuses the case structure for electrical reference purposes, avoiding the need for separate reference potential generation circuits and reducing overall device complexity
3Strength
If a protective sheet is used to cover the touch sensor, then the robustness is improved, but the spacing between the protective sheet and detector becomes difficult to maintain at a predetermined amount
Solution Approach 1:
The patent applies dynamics by making the reference potential adaptable rather than fixed. The AC signal connected to the case provides a dynamic reference that adjusts to varying spacing conditions between the protective sheet and detector. This dynamic reference potential compensates for spacing variations, allowing the system to maintain detection accuracy even when the predetermined spacing is difficult to maintain during manufacturing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces the likelihood of water being erroneously detected as a touch, allowing accurate detection of finger touches while minimizing errors with high relative permittivity substances, ensuring reliable touch input even in contact with substances like water.
Implementation Method 1
a signal generation circuit capable of applying an AC signal to a ground of the panel controller
Implementation Method 2
the panel controller measures a capacitance of the touch sensor
Data Source
AI summary
A display includes a touch sensor panel, a panel controller, a case, and a signal generation circuit. The touch sensor panel includes a touch sensor. The panel controller measures a capacitance of the touch sensor. The case accommodates the display, in which at least the touch sensor panel and the panel controller are disposed. The signal generation circuit is capable of applying an AC signal to a ground of the panel controller. The case is electrically connected to the ground of the panel controller. When the signal generation circuit applies the AD signal to the ground, the panel controller measures the capacitance of the touch sensor.